IGT Pick & Blister

(Traditional Inking Unit)

This test measures the ability of coated or uncoated paper or paperboard to resist picking or blistering during offset printing.  The test device operates by applying a known film thickness of polybutyne oil of a given viscosity to an aluminum printing disk.  The oil is applied to the disk with a standard IGT inking unit.   The oil is transferred to the sample surface while under acceleration (ie, the application speed increases from 0 m/s to 4 m/s during the application).  The oil creates a pulling action on the paper surface, like offset ink, resulting in picking, blistering, or both.  The point at which the picking and blistering starts is the end point of the test.  The reported units for both pick and blister are viscosity-velocity product (vvp).  At a known oil viscosity, this value relates to the velocity or press speed that can be achieved before the sheet is damaged.